Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (4): 455-460.doi: 10.11743/ogg20050410

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Types of cracking gas in Hetianhe gas field in Tarim basin

Qin Shengfei1, Li Mei2, Dai Jinxing1, Xiao Zhongyao2, Zhang Qiucha2   

  1. 1. Exploration and Development Research Institute, PetroChina, Beijing;
    2. Tarim Oilfield Company, PetroChina, Xinjiang
  • Received:2005-07-05 Online:2005-08-25 Published:2012-01-16

Abstract:

Natural gas in Hetianhe gas field,which is distributed in an elongated E-W direction as a whole,have been sourced by the high-and over-mature Cambrian source rocks.The components of natural gas in Hetianhe gas field have the following characteristics: C2/C3 decreases with increasing C1/C2,variation of carbon isotope value of δ13C213C3 is relatively large,while variation of ln(C2/C3) value is relatively small.According to the conventional diagnostic criteria of kerogen cracking gas and secondary cracking gas from oil,the gas in Hetianhe gas field should be of kerogen cracking gas.The dry coefficients,methane carbon isotope values and CO2 contents of natural gas are obviously different in the western and eastern wellblocks of Hetianhe gas field.Accompanying the formation of Hetianhe trap in late Himalayan,the kerogen cracking gas migrated from the high pressure zone in the east to the low pressure zone in the west in the form of dissolved gas.The solubility of methane in water is larger than that of heavy hydrocarbons,the solubility of δ13CH4 is larger than that of δ12CH4),and CO2 has the largest solubility among the components of natural gas,all these would lead to the fractionation of natural gas components and methane carbon isotope.As a result,the natural gas in the western wellblock is characterized by larger dry coefficient,heavier methane carbon isotope and obviously higher CO2 content.

Key words: Tarim Basin, Hetianhe gas field, cracking gas, water-soluble gas, migration

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